Our laboratory has been engaged in studies to determine the signal transduction pathway by which naturally occurring oxysterols induce apoptosis in various vascular cells, particularly macrophages. Our published results indicate that arachidonyl esters of these oxysterols are second messengers of the apoptotic response. In an effort to understand the mechanism by which these compounds entrain apoptosis we have begun to examine the hypothesis that arachidonyl oxysterols produce these effects via the cannabinoid 2 (CB2) receptor. Preliminary findings, presented in this proposal, of a loss of the apoptotic response to oxysterol treatment in various cell models defective in CB2 signaling are consistent with this hypothesis. Other studies from our laboratory indicate that one of the physiologically significant consequences of macrophage apoptosis in response to oxysterols is as a protective mechanism against atherosclerosis. This raises the possibility that CB2 signaling of apoptosis in macrophages may serve as one of the signaling pathways of this anti-atherosclerotic effect. To test these ideas regarding the mechanism and physiological significance of arachidonyl oxysterol signaling of apoptosis in macrophages we propose the following specific aims: 1) Determine if arachidonyl oxysterols can induce apoptosis in macrophages. 2) Determine if arachidonyl oxysterols can bind to cannabinoid receptors and modulate their activity. 3) Examine the role of the CB2 receptor in the development of atherosclerosis in mouse models. The results from this investigation may expand our understanding of the link between cannabinoid signaling mechanisms and the mechanisms regulating apoptosis in macrophages. They may also provide new pharmacologically exploitable targets for the development of novel pharmaceuticals for treatment of atherosclerosis. [unreadable] [unreadable] [unreadable]